Overweight Teens Don't Necessarily Consume More Calories

Overweight teens actually eat fewer calories daily on average than their trimmer counterparts, a new study finds.

Among 12- to 14-year-old girls in the study, girls who were very obese ate about 300 fewer calories on average daily than obese girls, and obese girls consumed 110 fewer calories daily than healthy-weight girls.

When the researchers looked at calories consumed by 15- to 17-year old boys, they found that obese boys ate about 220 fewer calories a day than boys who were overweight (but not obese). And overweight boys consumed about 375 fewer calories than healthy-weight boys, the study showed.

The findings illustrate the difficulty of losing weight by cutting calories alone, especially when the weight is gained early in life, the researchers said.

"For older children and teenagers, increasing involvement in physical activity may be more important to weight and health than is their child’s diet," said study researcher Asheley Cockrell Skinner, an assistant professor of health policy and pediatrics at the University of North Carolina at Chapel Hill. "Parents of all children should aim for a healthy diet, but don’t assume that overweight children are eating any worse than their peers," she said.

The findings may provide validation for overweight teens facing a frustrating reality: they eat less than their normal-weight peers, yet continue to weigh more.

"I think our findings are particularly important from a social perspective," Cockrell Skinner said. "It’s easy for society to make assumptions that kids are eating a lot of junk, which can also imply blame for their obesity, but the research doesn’t bear that out."

The findings are published online today (Sept. 10) in the journal Pediatrics.

Eating and obesity

More than a third of children and adolescents are overweight or obese, according to the Centers for Disease Control and Prevention (CDC).

In the study, Cockrell Skinner and colleagues analyzed data gathered from 12,650 U.S. children during the CDC's National Health and Nutrition Examination Survey between 2001 and 2008. They looked at the number of calories that children reported (for young children, their parents reported calorie intake) consuming daily, based on a detailed, two-day food questionnaire.

During a physical exam, researchers noted the children's heights and weights, and used this to calculate their body mass index (BMI). Based on their BMIs, children were considered to be healthy weight, overweight, obese or very obese.

Among young children, the researchers were not surprised to find that those who were overweight or obese generally ate more calories daily than healthy-weight children. For example, obese 3- to 5-year-old girls ate an average of 1,670 calories daily, whereas healthy-weight girls consumed 1,578 calories daily. Very obese 6- to 8-year-old boys ate 2,127 calories per day, whereas healthy-weight boys ate 1,978 calories.

However, around ages 9 to 11, the pattern turned around — children with higher BMIs ate less than their peers. Several factors contribute to why the change occurs around this age, Cockrell Skinner said.

"The body is a complex system, and once a person is overweight, the body tends to want to stay that way," she said. Kids of this age also start to have more control over what they are eating, she said, and may want to eat things similar to their friends.

The researchers also found, inline with previous studies, that overweight and obese children tended to be less physically active than healthy-weight kids.

What parents can do

The findings highlight the need to prevent obesity early in life, Cockrell Skinner said. With young children, parents should allow their child to determine when they are full, and not encourage overeating.

For weight-loss efforts in older children and teens, "focusing on activity may prove to be a more useful strategy than encouraging caloric restriction," the researchers wrote in their study. All parents should aim for their children to have a healthy diet, but not assume that overweight children are eating any worse than their peers, Cockrell Skinner said.

"I think the most important thing is that kids become more active," Cockrell Skinner said. "Even in the absence of any weight loss, activity is good for overall health, and cardiovascular health specifically."

A sharply reduction of children's calories are not good for their growing, developing bodies, and in addition, such diets aren’t sustainable when a child's peers are eating differently, she said.

"Being more active and making healthy food choices are very important to long-term health, and that’s the most important goal," she said.

Pass it on: Weight-loss efforts for overweight and obese teens should focus on increasing physical activity.

Karen Rowan

Karen came to LiveScience in 2010, after writing for Discover and Popular Mechanics magazines, and working as a correspondent for the Journal of the National Cancer Institute. She holds an M.S. degree in science and medical journalism from Boston University, as well as an M.S. in cellular biology from Northeastern Illinois University. Prior to becoming a journalist, Karen taught science at Adlai E. Stevenson High School, in Lincolnshire, Ill. for eight years.